Representatives from Her Majesty's Revenue and Customs visited Rangers on Thursday in pursuit of backdated tax payments. A Rangers source has confirmed that – as part of an ongoing process during which HMRC is claiming £4.2m – documents were delivered to Ibrox. Amid the paperwork was the threat that assets could be frozen or Rangers wound up if the liability was not met.

Rangers, who say they have already paid hundreds of thousands of pounds as part of the case in hand, are disputing the total amount due, which comprises £2.8m plus a £1.4m penalty, dating back to 1999. Rangers insist talks are ongoing with HMRC and that the government body is acting with undue haste.

The issue came to light as part of due diligence carried out by Craig Whyte before his recent purchase of Rangers. The club contest the £1.4m penalty largely on the basis of how the bill emerged and also because the figure owed relates to a previous Rangers regime.

The source said: "We find it appalling that this process is being played out like a soap opera by media leaks from HMRC. We are hugely frustrated that a business negotiation between the club and the taxman is entering the public domain."

A complication is that Rangers are already awaiting a significant tribunal with HMRC over employee benefit trust benefits to players. If that goes against them, the club could be liable for tens of millions of pounds. The affair is first due for a provisional hearing in court in Edinburgh in the next few weeks. HMRC says it will not comment on individual cases.